Diagnostische Verfahren bei der Hepatitis C und ihre Zuverlässigkeit. Reliability of diagnostic procedures for hepatitis C

Abstract

AbstractThe diagnosis of HCV infection is often hampered by false positive reactivities in antibody screening assays. Therefore, confirmatory assays are necessary. Since most unspecific reactivities are only slightly above the cut-off value, the intensity of the reactivity should always be considered. Particularly in groups with low HCV risk such as blood donors, positive reactivities obtained by one test system can often be ruled out by re-testing with another format (e.g. an enzyme immunoassay instead of a microparticle enzyme immunoassay). Most confirmatory assays are based on a recombinant immunoblot assay (RIBA); these tests should always be done in patients diagnosed as HCV positive for the first time. Additionally, in many cases, tests for HCV RNA are necessary. Based on these results, an evaluation of the risk of transmission to household contacts is possible and in patients receiving antiviral treatment, the success can be monitored. A negative PCR result in patients showing high positive antibody reactivities does not necessarily represent loss of the virus since even in chronic carriers, viral replication can be intermittently very low. Immuno-compromised patients often show prolonged seroconversion so that antibody screening assays remain negative for a long time while the patients have high level viraemia. Therefore, we recommend regular RT-PCR in populations at risk such as patients on chronic dialysis. To evaluate patients for antiviral treatment, the determination of the genotype is necessary. The HCV genotype also has an influence on the course of liver disease in chronic carriers. Possible transmission of HCV, e.g. by blood products, can be elucidated by sequence analysis of the high variance region (HVR) of the virus.